The present invention relates to a plumbing device for plumbing a surveying instrument and, more particularly, to a plumbing device for plumbing a surveying instrument, capable of calculating dislocations x and y of the surveying instrument from a datum point, and the instrument height H of the surveying instrument.
Generally, survey work is carried out with reference to a datum point. A survey instrument is set on a datum point or a given point and measurement is made from the datum point or the given point. For example, a theodolite has a sighting telescope mounted so that it is free to rotate around horizontal and vertical axes, and the sight directions of the sighting telescope are measured for survey. A leveling instrument is used for measuring the difference of height of a sight position.
These survey instruments are used on a tripod. Therefore, the height of the sighting telescope from the ground, i.e., instrument height necessary for calculating difference of elevation, must be measured.
FIG. 9 shows a surveying instrument 9100 mounted on a tripod 9000, and a surveying marker 9200. The surveying instrument 9100 is set so that its vertical rotation axis coincides with a vertical line passing a datum point. A reference point for measuring instrument height H is formed on a support coinciding with the center of horizontal rotation of a sighting telescope.
As shown in FIG. 10, the surveying instrument 9100 is provided with a leveling mechanism 9110 for aligning the tilted vertical rotation axis thereof with the vertical line, and a plumbing telescope 9120 for correcting the horizontal position thereof. A datum point lying under the surveying instrument 9100 on the vertical rotation axis can be viewed through a reflecting prism 9130 and the plumbing telescope 9120.
A surveyor installs the surveying instrument 9100 in alignment with the datum point, measures the instrument height H of the surveying instrument 9100, and measures the distance between the reference point on the support of the surveying instrument 9100 and the surveying marker 9200 with a measuring tape or the like.
When measuring the instrument height H of the conventional surveying instrument 9100, the distance between the point on a lower part of the surveying instrument 9100 and the surveying marker 9200, and the thickness of a mount and the height of the surveying instrument 9100 are added to the distance. Since the height of the surveying instrument 9100 is changed by leveling, the height of the surveying instrument 9100 needs to be measured when installing the surveying instrument 9100, which takes time and accurate measurement cannot be expected.
Usually, the distance between the reference point and the surveying marker 9200 is measured approximately and directly. In some cases, the reference point for measuring the instrument height H does not lie on the vertical line passing the datum point, and hence the accurate measurement of the instrument height H is impossible.
The surveying instrument 9100 must be set with its vertical rotation axis aligned with the vertical line passing the datum point to achieve accurate surveying and the accurate measurement of the instrument height H.
First the position of the surveying instrument 9100 mounted on the tripod 9000 is adjusted by the leveling mechanism 9110 so that the vertical rotation axis of the surveying instrument 9100 extend vertically. Subsequently, a screw, not shown, fastening the surveying instrument 9100 to the tripod 9000 is unfastened slightly while viewing the plumbing telescope 9120, and the surveying instrument 9100 is moved horizontally to bring the vertical rotation axis of the surveying instrument 9100 into alignment with the vertical line passing the datum point.
This adjustment work requires very high skill. An error is introduced into the level of the surveying instrument 9100 or the tripod 9000 is moved unless the adjustment work is carried out very carefully.
Recently, the measuring accuracy of the surveying instrument 9100 has remarkably improved, and the surveying instrument 9100 is capable of highly accurate survey. If a surveying instrument capable of measuring horizontal angles and elevation angles in an accuracy of about 5xe2x80x3 is dislocated from a plumb position by 5 mm, an error of about 10xe2x80x3 per 100 m is introduced in the measurement of the surveying instrument. Therefore the plumbing work requires highly accurate work of a skilled surveyor. Accordingly, there has been an ardent desire for a means capable of enabling persons other than skilled persons to achieve the highly accurately measurement of the instrument height H.
Accordingly, it is an object of the present invention to provide a plumbing device for plumbing a surveying instrument capable of calculating dislocations x and y of the surveying instrument from a datum point, and the instrument height H of the surveying instrument.
According to one aspect of the present invention, a plumbing device for plumbing a surveying instrument, capable of calculating the instrument height H of the surveying instrument comprises optical means for forming an image of a target placed at a survey station to indicate the station; photodetecting means for receiving an image of the target and providing an image signal, and processing means for calculating instrument height corresponding to the distance between a reference point on the surveying instrument and the target and dislocation from the station.